Applied Mechanics and Materials Vols. 433-435

Abstract: Dynamic load is a key consideration in large scale wind turbine design. It is approved that the performance of controller can distinguish impact wind turbine loads. For strong external disturbances and inaccurately modeled of large wind turbines, In this paper, we propose model-free adaptive (Model Free Adapt, MFA) individual pitch control algorithms. The controller was developed in to mitigate the rotor unbalance structural load for variable speed wind turbine. The controller is designed from a nonlinear model of the system which takes into account the blades, shaft and tower flexibilities. Bladed software was used for the control strategy and traditional PID control strategy simulation comparison. The results show that the new control strategy can effectively stabilize wind turbine power output and reduce aerodynamic loads.

Abstract: The classic voltage space vector PWM (SVPWM) is a kind of symmetrical regular-sampled PWM with zero sequence component added to its modulating wave. The technique of carrier phase shifted SPWM (CPS-PWM), which combines the multilevel with SPWM technique, is characteristic of high equivalent switching frequency of the output wave. A technique named sample time staggered SVPWM which combines SVPWM with CPS-PWM is presented in this paper. In order to reduce the maximum switching current, the zero sequence component added into the individual converter units can be adjusted dynamically according to the phase of the load current. Thus, the non-switching sectors can be arranged close to the period of the maximum load current. So the maximum switching current in each element can be reduced effectively and the minimum switching losses of the multi-modular converter are achieved. Simulation results implemented by PSCAD/EMTDC show the validity of the proposed approach.

Abstract: Analyzed working principle of servo control system and applications of direct current (i.e. DC) servo motor in the two-dimensional (i.e. 2D) digital control system, used embedded PC104 processor as the central processing unit, selected DC servo motor whose model was J320LYX04C as azimuth axis motor, and DC servo motor whose model was J215LYX03E as pitch axis motor, constituted the executive body for servo system, and designed a driving and control system which can control the two-dimension turntable rotating precisely in space and lead CCD image sensor to catch and track target. Tests show that the system positioning accuracy meet the given requirements and the system with high reliability runs smoothly in the real application.

Abstract: In this paper, according to the splitting criterion ucosφ, the effectiveness and boundedness of the improvement method is studied. As the oscillation center may be an isolated dot or exists in a section of the splitting, this paper has proposed the thought of false oscillation center and introduced the relative degree coefficient of oscillation k which reflects the degree of effect on the tie lines. The tie lines being cut off should be sorted based on the value of k. If the system recovers stable, the tie lines remained should not be cut off. It is vital to the control of the splitting and reducing the losses of accidents. In the end, the simulation is given in the IEEE 10 Generator 39 Bus System which proves the correctness and effectiveness of this method.

Abstract: Recently, the static synchronous compensator (STATCOM) device has been installed in Jiuquan wind farm in Gansu Province. To study its ability to support voltage, this paper presents a study of the mathematical model of the steady state and transient state of STATCOM and then uses the power system analysis software package (PSASP) to establish a user-defined model of STATCOM. In addition, the model is added into the power system example (CEPRI 7). After that, the power flow calculation and transient stability calculation are carried out to simulate and analyze. At last the STATCOM device is field tested in Jiuquan wind power base. Test results verify that STATCOM effectively supports the grid voltage.

Abstract: With the application of FACTS devices in large-scale new energy base, in the light of FACTS devices installed in each wind farm in Gansu Jiuquan, which can supply reactive compensation for the power transmission system and stable the grid voltage, in this paper the magnetic controllable reactor (MCR) type static var compensator (SVC) is studied deeply. The paper introduces the working principle and characteristics of the MCR-SVC. In connection with MCR equivalent circuit, the simulation model is built in MATLAB/SPS, the simulation results and field tests verify the reactive power compensation effect of MCR-SVC during wind farms.

Abstract: Under the influence of the view that reactive power compensation on-spot, the study on control of reactive power and voltage in wind farms focused on a single wind farm optimal reactive voltage control. China's wind power resources are relatively concentrated and a region often have several or even a dozen wind farms. Wind farm thought as a unit to adjust often leads to irrational reactive power flow. Wind farm groups and collection substations must be thought together as a whole to manage. This paper makes use of collection substations to support area voltage, coordinates reactive power output of the wind farm groups based on the voltage sensitivity and improves the overall grid voltage level of the wind farm groups areas. Simulation results proved that the program can improve the regional power grid voltage level.

Abstract: This paper presents a novel control method combining based adding SOC (state of charge) feedback to change the time constant of the low pass filter to smooth the power and based proportional algorithm to control frequency fluctuations for keeping wind power smoothing and frequency fluctuation to a minimum. Building models of wind power system and BESS(battery energy storage system) in Matlab/Simulink. The simulating results indicated that the proposed wind power generation-storage system could supply steady output power, and could participate in the power grid frequency control.

Abstract: A new model based on optimal feedback gain has been proposed for the power system decentralized control. In this model, the block gain coefficient has been optimized to achieve excitation decentralized coordinated control of the multi-machine power system. The simulation of the Henan Yudong grid verified the effectiveness of the control strategy.

Abstract: Along with the government and market take more and more attention to the energy efficiency of power supply, the loss of IGBT module, as the core device, has become a hot topic. Firstly, the dynamic process of IGBT module is analyzed, an accurate and an estimation method of loss calculate are provided, then the working process and resonant process of phase shift full-bridge soft switching converter is discussed, and constitute of IGBT module loss in the circuit is analyzed. Finally the loss is calculated in the 350A inverter welder example, and a conclusion of reliability and proposal for design are given according to the calculation results.